In the prior art, various solar battery modules and solar battery panels have been implemented in practice that incorporate solar cells installed in a window material capable of transmitting sunlight. Generally, these are silicon type solar battery modules (or panels) that are made by laying flat plate shaped silicon solar cells that are manufactured from wafer shaped silicon crystals between two glass plates. Such a module is an adhered structure that is made by lining up the solar cells in a planar configuration with appropriate gaps being left between them and electrically connecting the cells by ribbon shaped conductors, and then by embedding them in the gap between the two glass plates using an EVA (ethylene vinyl acetate) resin.
Furthermore, there is a thin layer type of solar battery module in which are made from amorphous silicon and microcrystalline material. In order to manufacture such module as a window material, first, a transparent electrode layer of TCO (SnO2) is formed on a glass substrate, and is separated into sections by laser light for making cell electrode portions. Next, a thin silicon layer, amorphous silicon (a-Si), and a thin silicon microcrystal layer are sequentially laminated thereupon, and this photoelectric layer is separated into sections at a constant pitch by laser light. Furthermore, a thin metallic layer is adhered over the entire area of the rear surface serve as an electrode, and, again with laser light, this metallic layer is separated into mutually insulated portions, so that a large number of small thin-layer solar cells are electrically connected in series at one time.
With these solar battery modules described above, only one side of the solar cells can serve as a light reception surface, and the electricity generation capability is low because the usable range of ambient light around the module is narrow. Furthermore, with a silicon type solar battery module, the see-through ratio (sunlight transmission ratio) become small due to the flat plate type solar cells which are large in size. Moreover, with a thin layer type solar battery module, the thin layers on the glass substrate is accompanied by many difficulties.
In Patent Document #1, there is disclosed a rod type solar cell in which a rod shaped crystal of small diameter is made in order to reduce the processing loss of semiconductor material, and, after this crystal has been cut into an appropriate length, there are manufactured a pn junction of partially cylindrical shape that is formed to a constant depth along the surface of the rod shaped semiconductor and a pair of small positive and negative ribbon shaped electrodes that are provided at the central portion of the surface of the rod shaped semiconductor so as to oppose one another on opposite sides of its center. But, since this cell is used by being fitted at the focal point of a mirror light condenser, its reception of light is limited to the light in front of the mirror. Furthermore, as in Patent Document #2, the present inventor has also proposed a rod type solar cell, on a portion of which a flat surface is formed. This rod type solar cell is made so as individually to receive all the incident light in 360° around an axis. Due to this, this rod type solar cell is compact and can be manufactured simply and also at a low price, as compared to the silicon type solar cell and the thin layer type solar cell described above.
Since in a module in which this rod type solar cell is installed the front surface of the cell is a cylindrical surface, which is different from the case of one to which a mirror light condenser is attached as in the case of Patent Document #1, it is possible to receive light over a range of almost 360° with respect to the central axis of the rod, and this advantage is very clear in an environment in which not only directly incident light is present, but also there is a lot of reflected light and scattered light. For example, if this cell is housed in a transparent package, then light that is reflected and scattered in the interior thereof can also contribute to generation of electricity, so that, if such a solar battery module is installed vertically in a building such as an office building or the like and also serves as a window, it is possible for it to also absorb reflected light from the ground surface or neighboring buildings or the like and generate electricity thereby. Moreover since the light reception surface is a cylindrical surface, although the angle of incidence for direct illumination from the sun changes according to the time of day, nevertheless it is still possible to anticipate comparatively stable electricity generation that does not depend on the direction of incidence, as compared with the planar type of solar cell or the type described in Patent Document #1.                Patent Document #1: U.S. Pat. No. 3,134,906.        Patent Document #2: International Publication WO 2007/144944.        